The invention relates generally to lighting devices, and more particularly to organic electronic devices.
Currently, organic electronic devices, such as, but not limited to, organic light emitting diodes (OLEDs), are being increasingly employed for display applications and for lighting applications. In the last decade, tremendous progress has been made in the area of OLEDs. Previously, liquid crystal displays (LCDs) were employed for most display applications. However, the LCD displays involve high production and commercial expenses.
With the imaging appliance revolution underway, the need for more advanced devices that provide advanced display and/or lighting features is increasing. Further, it is often desirable to combine the attributes of a computer, personal digital assistant (PDA), and cell phone, along with the aforementioned display and/or lighting features. In addition, the need for new lightweight, low power, wide viewing angled devices have fueled an emerging interest in developing flat panel displays while circumventing high production and commercial expenses associated with liquid crystal displays. Consequently, the flat panel industry is looking to employ new displays such as OLEDs.
As will be appreciated by one skilled in the art, the OLED includes a stack of thin organic layers sandwiched between two charged electrodes. The organic layers include a hole injection layer, a hole transport layer, an emissive layer, and an electron transport layer. Upon application of an appropriate voltage to the OLED lighting device, where the voltage is typically between 2 and 10 volts, the injected positive and negative charges recombine in the emissive layer to produce light. Further, the structure of the organic layers and the choice of anode and cathode are designed to maximize the recombination process in the emissive layer, thus maximizing the light output from the OLED device. This structure eliminates the need for bulky and environmentally undesirable mercury lamps and yields a thinner, more versatile and more compact display or lighting device. In addition, OLEDs advantageously consume relatively little power. This combination of features enable OLED displays to advantageously communicate information in a more engaging way while adding less weight and taking up less space. Further, this combination of features may also provide smaller, lighter and more versatile devices used for area lighting applications.
However, the development of large area OLEDs is difficult due to failures of the OLED devices owing to the presence of local defects that cause electrical shorts and electrical opens. Typically, particle contamination during fabrication, asperities from electrode roughness and non-uniformities in organic layer thickness may cause shorting between the anode and cathode of the OLED. Also, a loss of electrical connectivity in an OLED may cause an electrical open.
It may therefore be desirable to develop a robust device architecture that advantageously provides fault tolerance against both electrical shorts and electrical opens.